Abstract
As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). Anthropogenic spheroidal aluminosilicates clearly identify the beginning of industrial development and are proposed as a new indicator of the Anthropocene. In cal AD 1963 (±5), greatly elevated dust deposition and an increase in REE serve to show that the geochemistry of elements in the peat can be evidence of nuclear weapon testing; such constituted an enormous force blowing soil dust into the atmosphere. Among the natural dust sources, minor signals of dryness and of the Tunguska cosmic body (TCB) impact were noted. The TCB impact was indirectly confirmed by an unusual occurrence of mullite in the peat.
Highlights
Ombrotrophic peatlands are a well-known trap of atmospheric dust, trace elements and pollutants[1,2,3,4] originating from both natural sources[5,6,7,8] and anthropogenic sources[1,9,10,11,12,13]
The human influence on the amount and composition of atmospheric dust deposited on Mukhrino peatland can be seen to start in the late 1950 s (Figs 2 and 3)
Less negative epsilon Nd values and lower 87Sr/86Sr values in modern Chinese dust is ascribed by Li et al.[20] as due to possible addition of anthropogenic particles
Summary
The human influence on the amount and composition of atmospheric dust deposited on Mukhrino peatland can be seen to start in the late 1950 s (Figs 2 and 3). Decreasing enrichment factors for Cu, Ni and Zn reflect the insignificance of pollution from heavy industry at that time in Mukhrino (Fig. 3) These observations further strengthen the point that nuclear tests were the reason for the first human-induced increase in dust fallout in Western Siberia. A depth to water table (DWT) reconstruction based on testate amoebae[35] shows that dry conditions dominated up to cal AD 1750 (±62), with a maximum at the turn of 15th and 16th centuries (Fig. 2) This was followed by low carbon accumulation rates (CAR), declined signature of epsilon Nd (−8,5) and elevated 87Sr/86Sr (0.712061 ± 0.000010), similar to the signature of Chinese loess (Table 1; Sr and Nd isotopic data not available for Siberian loess). In addition to the release of radionuclides, the accumulation rate and enrichment of REE can be an important indicator defining nuclear tests as drivers of increased atmospheric dust
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